*R*_{mean} **(***X*_{mean}**)** | Mean resistance (reactance) during total breaths |

*R*_{meanE} **(***X*_{meanE}**)** | Mean expiratory resistance (reactance) |

*R*_{meanI} **(***X*_{meanI}**)** | Mean inspiratory resistance (reactance) |

**EFL index**^{#} | *X*_{meanI} – *X*_{meanI} |

*R*_{eE} **(***X*_{eE}**)** | Resistance (reactance) at end-expiration |

*R*_{eI} **(***X*_{eI}**)** | Resistance (reactance) at end-inspiration |

**Δ***X*_{I} | *X*_{eE} – *X*_{eI} |

*X*_{min} | Minimum expiratory reactance |

**AXV** | Area within the reactance *versus* volume loops |

*V*′_{maxE} | Maximum expiratory flow |

*V*′_{maxI} | Maximum inspiratory flow |

*T*_{E} | Expiratory time |

*T*_{tot} | Breathing period |

*T*_{PTEF} | Expiratory time until peak expiratory flow |